1. Field of the Invention
The present invention relates to a method for controlling a light emitting portion for a liquid container as well as a printing apparatus, and more specifically, to a method for controlling a light emitting portion for a liquid container which can individually control light emitting portions such as LEDs provided in a plurality of liquid containers, and a printing apparatus using a plurality of liquid containers comprising light emitting portions.
2. Description of the Related Art
With the recent prevalence of digital cameras, printers (printing apparatuses) have more often been connected directly to digital cameras without the mediation of PCs (Personal Computers). Moreover, card type information storage media for digital cameras have more often been installed directly in printers so that data in the information storage media can be transferred to the printer for printing (non PC printing).
As a method for determining the amounts of ink remaining in ink tanks (liquid containers) provided in a printer, a technique is well known which checks the amount on a monitor via a PC. In connection with the non PC printing, there has been a growing need to determine the amounts of ink remaining in the ink tanks without the mediation of the PC. By determining that only a small amount of ink remains in an ink tank, users can replace the ink tank with a new one, for example, before starting printing. This makes it possible to prevent a printing operation from being substantially disabled by the insufficient amount of ink before the operation is completed.
A configuration using display elements such as LEDs has been known as means for reporting such a condition of the ink tank to the user. Japanese Patent Application Laid-Open No. 4-275156 describes a configuration in which two LEDs are provided for each of the ink tanks integrated with a print head to illuminate at two levels depending on the ink remaining amount. Japanese Patent Application Laid-Open No. 2002-301829 also describes a configuration in which each ink tank is provided with a lamp that illuminates depending on the ink remaining amount. Japanese Patent Application Laid-Open No. 2002-301829 also describes a configuration in which each of four ink tanks used in the printing apparatus is provided with a lamp that indicates the ink remaining amount.
On the other hand, the need for the improved quality of printed images has led to the use of ink such as light magenta or cyan which has a lower concentration, in addition to conventional four colors (black, yellow, magenta, and cyan). Moreover, what is called special color ink such as red or blue has more often been used. More ink tanks are now mounted in printers in association with the types of inks used.
Owing to manufactural variations among light emitting portions using light emitting elements such as LEDs, the quantity of emitted light varies among the plurality of LEDs even if the same current is passed through the same circuit. Thus, if LEDs are provided for the respective ink tanks provided in the printer, the quantity of light emitted by these LEDs may vary.
The ink tank may be provided with a light emitting portion, a light guiding portion, and a display portion so that light from the light emitting portion is guided through the light guiding portion to the display portion located where it is easily seen by the user. However, in this case, manufactural variations among the light guiding portions may vary their light guiding characteristics and thus the quantity of light guided from the light emitting portion to the display portion. For example, it is assumed that the printer has a mixture of ink tanks with LEDs illuminating brightly and ink tanks with LEDs illuminating darkly and that the LEDs provided in the plurality of ink tanks are all blinking. In this case, the user may erroneously determine that a large amount of ink still remains in the ink tanks with the LEDs illuminating brightly and that only a small amount of ink remains in the ink tanks with the LEDs illuminating darkly. The users may thus determine that a variation in brightness among the LEDs for the ink tanks has some meaning. This may impair the functions of the reporting means using the LEDs.
The recent printers are also desired to consume reduced power for an ecological reason. Moreover, since portable computers called a notebook type are commonly used as PCs (Personal Computers) serving as host devices, mobile printers have appeared which can be connected to these-notebook PCs. Many mobile printers need to be driven by a limited power source such as batteries instead of a common domestic power source that can be inexhaustibly used by printers. Thus, electronic control modules constituting these mobile printers are desired to further save power.